The present invention relates to a manufacturing method and a manufacturing device for an optical recording medium having a high density, onto and from which information can be recorded and reproduced by using a laser beam, and more particularly concerns a manufacturing method and a manufacturing device for an optical recording medium capable of recording only once; that is, a so-called write-once type optical recording medium or an optical recording medium, such as CD-Rs and DVD-Rs.
In recent years, optical recording media have been widely used because of their high information density and ease in retrieving data. In particular, CD-Rs, which have a large capacity (650 MB) and are of comparatively low cost, have recently been extensively used. An explanation will be given of manufacturing methods and products of the optical recording media.
FIG. 1 is a schematic cross-sectional view, taken perpendicularly to the round face of a disk, of a conventional manufacturing device for forming a recording layer of a write-once type optical recording medium. This device is referred to as a spin coater.
In this Figure, reference numeral 10 is a spin coater main body, 12 is a substrate for the optical recording medium, 14 is a spindle shaft, 16 is a spindle table, 18 is an application nozzle for a recording layer solution, 20 is an organic pigment solution of a recording layer material, and 22 is a spindle motor. The organic pigment solution of the recording layer material 20 is supplied onto the optical recording medium substrate 12 through the nozzle 18. Thereafter, when the spindle motor 22 rotates in the direction of the arrow 24, the optical recording medium substrate 12 on the spindle table 16 is allowed to rotate at the same time, and the solution of the recording layer material 20 expands in the direction of the arrow 26 so that the solution of the recording layer material 20 is applied onto the optical recording medium substrate 12 with a uniform thickness. The organic pigment contained in the solution of the recording layer material 20 is made of a material such as a phthalocyanine pigment and a cyanine pigment.
FIG. 2 schematically shows a cross-sectional structure, taken perpendicularly to the round face of the disk, of one portion of an optical recording medium manufactured by the above-mentioned manufacturing method. In this Figure, reference numeral 28 is a minute groove provided on the surface of the optical recording medium substrate 12, 30 is a recording layer, 32 is a reflective layer, and 34 is a protective layer. When the solution of the recording layer material is applied as described above, the solution of the recording layer material fills the minute groove 28 of the optical recording medium substrate made of polycarbonate. The solution that has been applied is dried; and thus, the recording layer is formed. The minute groove 28 is of a spiral form extending from the inner circumference of the optical recording medium substrate 12 to the outer circumference thereof.
When information is recorded on such an optical recording medium as described above, a laser beam spot 36 is irradiated onto the groove 28 from a recording device so that the pigment material of the recording layer is decomposed and/or modified, or in some cases, the substrate 12 is deformed by heat generated at this time, with the result that a pit 38 is formed.
Upon irradiation of a reproducing laser beam with an output power lower than that of the recording laser beam, the reproducing laser beam is allowed to be reflected by the reflective layer 32 formed by sputtering gold or silver. However, compared with portions that have not been subjected to the laser beam at the time of recording, the light reflection coefficient of the pit 38 is lower so that this contrast due to the difference between the reflection coefficients indicates the presence of a signal. With this mechanism, the same signal output as that of the CD disk standardized by the Red book is obtained, so that the signal is identified as a CD one. The contents explained here are the same as those standardized for the write-once optical recording medium of the CD-R in the Orange book.
Although the manufacture of the optical recording medium by the use of the above-mentioned spin coater is comparatively simple, this method has various problems.
First, the characteristics of the organic pigment solution of the recording layer material 20 (for example, viscosity, etc.) are highly susceptible to external factors (for example, temperature, moisture, etc.), and the applied states of the solution are not the same between the inner circumference and the outer circumference of the optical recording medium depending on the number of revolutions of the spin coater and the controlled states of the number of revolutions. This results in the film thickness of the applied solution tending to have a difference between the inner circumference and the outer circumference of the optical recording medium; and therefore, it is not easy to form a recording layer having a uniform film thickness over the substrate.
Moreover, the organic pigment solution of the recording layer material 20 is applied by using various solvents, and in general, it is necessary to sufficiently dry the solution after having been coated. Since this drying process takes a long time, it is difficult to form the recording layer in a short time with high yield, which has been a problem in reducing the production costs of the optical recording medium.
In addition, as demands for high density of the optical recording media have increased, applicability to a short wavelength laser beam (for example, 650 nm) has been demanded, and various demands, such as, for example, capability of reproducing information by a DVD player (that is, compatibility with DVD players), which information has been recorded by using a long wavelength (780 nm in the case of CDs), and improvements of the organic pigment suitable for shortened wavelengths of the laser beam, are presented. Thus, methods such as the use of laminated organic pigment layers have been proposed.
However, the above-mentioned spin coat method has a problem in which a layer that has been first applied tends to be damaged by a solution of a recording layer material that is applied later at the time of rotation at high speeds. Moreover, size reduction of the pitch between grooves has been proposed in order to achieve the high density.
The above-mentioned conventional method has a limitation in its capability for solving these problems.
The present invention provides a manufacturing device of an optical recording medium for solving the above-mentioned problems. Specifically, the present invention provides a device for manufacturing an optical recording medium comprising a plurality of recording layers on a substrate, which device comprises a vacuum pre-treatment chamber, a plurality (at least two) of recording layer forming a chambers each for forming a recording layer by vapor deposition, a reflective layer forming chamber and a vacuum post-treatment chamber. Each recording layer forming chamber is provided with at least one recording layer forming unit, and the reflective layer forming chamber is provided with at least one reflective layer forming unit.
The optical recording medium manufacturing device of the present invention further comprises a substrate transporting mechanism, and this mechanism transports the substrate between chambers in the device. Therefore, by the substrate transporting mechanism, the substrate for the optical recording medium, which has been carried into the vacuum pre-treatment chamber inside the device, is transported from the vacuum pre-treatment chamber, through the recording layer forming chambers and the reflective layer forming chamber, to the vacuum post-treatment chamber, and discharged from the vacuum post-treatment chamber.
As will be described later, for example, in an embodiment in which the respective chambers are adjacent to each other, the substrate can be transported from one chamber to another chamber adjacent thereto inside the device. Moreover, in another embodiment in which the respective chambers are placed on the periphery of a rotary chamber, the substrate can be transported from one chamber inside the device to any chamber inside the device through the rotary chamber. In either of the embodiments, such a transporting process of the substrate is carried out by the substrate transporting mechanism.
Furthermore, the substrate transporting mechanism is preferably designed so as to transport the substrate for the optical recording medium from the outside of the optical recording medium manufacturing device into the vacuum pre-treatment chamber, and also to transport the substrate from the inside of the vacuum post-treatment chamber to the outside of the optical recording medium manufacturing device.
Moreover, the present invention also provides a method for manufacturing the optical recording medium by using the above-mentioned manufacturing device for the optical recording medium of the present invention. In other words, in the method for manufacturing the optical recording medium of the present invention that uses the optical recording medium manufacturing device having a vacuum pre-treatment chamber (or vacuum front chamber), a plurality (at least two) of recording layer forming chambers, a reflective layer forming chamber and a vacuum post-treatment chamber (or vacuum rear chamber), the substrate is loaded into the device from the outside thereof, allowed to pass through these chambers, and taken out of the device so that a plurality of recording layers are formed on the substrate by vapor deposition and a reflective layer is also formed on these recording layers. The transportation of the substrate inside the device is performed by using the substrate transporting mechanism. In a preferred embodiment, the loading operation of the substrate into the device and the discharging operation of the substrate from the device are also carried out by the substrate transporting mechanism.
In the above-mentioned device and method, the xe2x80x9csubstratexe2x80x9d maybe a substrate for an optical recording medium itself or a substrate holder supporting a plurality of such substrates.
The following description will explain various features of the present invention in association with various elements constituting the device of the present invention, and the explanations also apply to the method of the present invention, as well as to the device used in the method.
In accordance with the present invention, an optical recording medium comprising a substrate and a plurality of recording layers laminated thereon by vapor deposition is obtained by using only a single device; and these recording layers have an improved uniform thickness as compared with the formation of the recording layers by the use of the above-mentioned spin coater. The optical recording medium obtained by the present invention includes a plurality of the recording layers so that different or novel optical characteristics (for example, the spectral reflection coefficient characteristics with respect to the entire substrate), which have not been achieved by the conventional recording medium having only a single recording layer, can now be obtained.
For example, the optical recording medium obtained according to the present invention has a comparatively small spectral absorption coefficient not only to a light beam having a wavelength suitable for CDs (for example, 780 nm to 830 nm), but also to a light beam having a shorter wavelength (for example, 620 nm to 690 nm suitable for DVDs); and therefore, the optical recording medium obtained by the present invention is capable of dealing with two kinds of wavelengths (for example, CD-use wavelengths and DVD-use wavelengths).
The optical recording medium obtained by the device or the method of the present invention is provided with a plurality of the recording layers as described above so that unrecorded portions (that is, portions not irradiated with a recording laser beam) exhibit the different or novel optical characteristics as described above. Moreover, in recorded portions (that is, portions irradiated with the recording laser beam), at least one of the recording layers is allowed to mainly function as its inherent recording layer in the optical recording medium so that the pigment material forming the recording layer is decomposed and/or modified by the irradiation of the laser beam, resulting in a change in the optical characteristic of the recording layer, while the other recording layer(s) exhibit an assisting function for aiding such a change in the optical characteristic (which may be referred to as a recording assist layer). In some cases, of course, all the recording layers are decomposed and/or modified by the recording laser beam so that all the layers have both of the functions as the recording layer and the recording assist layer. It is difficult to clearly distinguish the functions of these recording layers and recording assist layers, and the plurality of recording layers are integrally allowed to exhibit a novel or different optical characteristic by the synergistic effect. From this point of view, in the present description, although all the layers formed in the recording layer forming chambers are referred to as xe2x80x9crecording layersxe2x80x9d for convenience of explanation, in addition to the so-called recording layer (the recording layer used in a normal optical recording medium), these recording layers include various layers functioning as recording assist layers for aiding the function of the recording layer, such as a filter layer and an enhance layer.
In the device of the present invention, since a reflective layer is formed after the formation of the recording layers, the time required for manufacturing the optical recording medium can be shortened. Furthermore, as will be described later, the device can manufacture the optical recording medium more efficiently by using a film-thickness measuring device, a shutter mechanism installed between the substrate and the recording layer forming unit (more preferably, combined with the film-thickness measuring mechanism), a rotation/rotation-revolution mechanism for the substrate, a mechanism for changing the positional relationship between the substrate and the recording layer forming unit (more preferably, combined with the film-thickness measuring mechanism), and a substrate transporting mechanism using a single-hand robot.
FIG. 3 schematically shows the optical recording medium thus manufactured in a cross-sectional view in the same manner as in FIG. 2. The optical recording medium 40 comprises a substrate 41 for the optical recording medium made of a material such as a polycarbonate, a plurality of recording layers 43 and 44 containing organic pigment materials laminated on the substrate 41, a reflective layer 45 formed on the recording layers, and a protective layer 46 formed on the reflective layer. The substrate 41 is provided with spiral grooves 42 formed on one surface thereof. The organic pigment materials forming the recording layers are desirably selected from, for example, phthalocyanine materials. In the device of the present invention, the recording layers 43 and 44 and the reflective layer 45 (that is, a portion 49) are formed on the substrate 41.
With respect to the material of the substrate 41 not being particularly limited, any material that is applied to a commonly-used optical recording medium and has a transmitting property with respect to laser light used for the optical recording medium is adopted. For example, plastic materials such as a polycarbonate and an acrylic resins are used.
With respect to the reflective layer 45, any material such as gold, silver or aluminum, may be used as long as it has a predetermined reflection coefficient, and those materials generally used for the reflective layer of the optical recording medium can be used in the present invention.
With respect to the protective layer 46, in the same manner as the reflective layer, a UV setting resin generally used for the optical recording medium may be used, and the resin is applied on the recording layer and set so as to form the resin layer. The protective layer is formed by applying and setting the resin after the recording layers and the reflective layer have been formed on the substrate in accordance with the present invention. A generally used protective-layer forming device may of course be combined with the device of the present invention.
FIG. 4 shows the results of measurements of the thickness of the recording layer of the optical recording medium manufactured by the vapor deposition in this manner. For the recording layer, a phthalocyanine compound was used as the pigment material, and the pigment material was heated to 150 to 250xc2x0 C. and evaporated under a condition of not more than 1xc3x9710xe2x88x923 torr, and vapor thereof was deposited on the substrate. After the recording layer had been formed on the substrate, the thickness of the recording layer was measured at predetermined portions by using a film thickness measuring device.
In FIG. 4, the axis of abscissa represents the radius of an optical recording medium having a diameter of 120 mm, and the axis of ordinate indicates the thickness of the recording layer. The solid line shows the film thickness of the recording layer formed by vapor deposition in accordance with the present invention at a radius position of 25 mm to a radius position of 57 mm. This shows that a recording layer having a very uniform thickness is formed by the vapor deposition method. The broken line in FIG. 4 shows the distribution of the thickness along a radial direction of the recording layer formed by using the spin coater.